The present invention relates generally to boring and reaming tools, and is particularly directed to a radially-adjustable tool that may form or ream a bore having a relatively high length-to-diameter ratio.
In some conventional machining center rotating tools, lubricant is supplied to the vicinity of the cutting blade through the rotating shaft. An example is shown in U.S. Pat. No. 5,775,853 issued on Jul. 7, 1998, the disclosure of which is herein incorporated by reference. Another example is shown in U.S. Pat. No. 6,270,295 issued on Aug. 7, 2001, the disclosure of which is herein incorporated by reference. Yet another example is shown in U.S. patent application Ser. No. 10/654,328 filed on Sep. 3, 2003, the disclosure of which is herein incorporated by reference.
In many machine tool operations, including boring and reaming, the friction between the tool and workpiece may generate tremendous amounts of heat energy, which may reach temperatures of 2000° F. (1100° C.) and above. If left uncontrolled, such heat may severely damage (e.g., crack or otherwise fracture) the tool, thus reducing the tool life, making machine tool operations more dangerous and expensive, and reducing the quality and precision of the workmanship. In addition, heat-generated friction may discolor the workpiece, and may damage or remove temper or heat treatments. It is commonly known in the industry that coolant and/or lubricant may be introduced to the machining area, such as by spraying, to reduce friction between the tool and workpiece by providing such fluid between the cutting tool and the workpiece (e.g., at the tool-workpiece interface), to thereby help remove heat energy generated in machine tool operations.
Although coolant/lubricant fluid may be supplied to the machining area, it is often difficult to ensure that such fluid actually makes its way to the interface between the tool and all of the workpiece surfaces being machined. Additionally, fluid may evaporate quickly due to the high temperatures involved in machining operations. Thus, large volumes of coolant/lubricant fluid must generally be continuously supplied to the machining area for the tool to operate effectively. This need to keep coolant/lubricant fluid between the tool and wall of the bore hole may become even more problematic in operations where coolant/lubricant fluids cannot be introduced in close proximity to the machining areas while the tool is engaged with the interior surface of the workpiece. This problem may arise in the context of producing any type of bore, including a bore having a relatively high length-to-diameter ratio.
During use, the work engaging surface of the tool (e.g., a cutting blade or a support member opposing a blade) may also become loaded with particles or recently cut chips from the interior surface of the workpiece, which in turn, may reduce the accuracy and effectiveness of the tool through deteriorating machining ability, and/or clogging of conventional coolant/lubricant fluid supply openings. It may be preferred that the potential for this loading of particles be reduced, and that any loaded particles be removed from the tool as quickly as possible. Nozzle arrangements, such as an external cleaning jet, may be provided independent of the tool, for injecting coolant/lubricant fluid at increased velocities toward the work engaging surface and the work surfaces of the workpiece to wash away particles, to remove particles already loaded on the work surface, and to cool the tool and the workpiece. As mentioned before, it may be very difficult to ensure that the fluid sprayed in this way actually reaches the most critical areas of the tool/workpiece interface.
Other attempts to deliver coolant/lubricant fluid to the machining area have included air or other pneumatic carriers. As with externally applied liquid coolants/lubricants, when pneumatic carriers are used, resulting turbulence may hinder the machining operations, and often fluid cannot infiltrate into the actual machining area. Previously, attempts to address these two requirements of cooling and cleaning the tool and workpiece have tended to reduce the accuracy and utility of the tool.
As can be seen, many conventional tools have a number of shortcomings that may greatly reduce the accuracy of the tool, the tool's life, or its ability to be used with automatic tool changing systems. Many conventional structures and assemblies provide a tool having working surfaces that cannot expand to accommodate varying and different uses and needs. Such assemblies may result in uneven machining, and may reduce the assembly's usable life. A need currently exists in the machinery industry for a tool with a work engaging assembly having accurately controlled machining diameters so that bores of different sizes may be cut or reamed by the same tool, so that the tool should not become oversized as a result of excessive strokes of the tool, and so that the tool may expand in a radial direction uniformly and selectively.
In addition, those of ordinary skill in the art will appreciate the variety of challenges associated with forming bores of high length-to-diameter ratios, such as a length-to-diameter ratio of 5:1 or higher, for example. These challenges may be even greater when high precision of the bore diameter is desired, and particularly when it is desired that many bores be produced by the same tool in a relatively short period of time. As a practical matter, many conventional tools used for larger bores cannot be feasibly scaled down for use in the production of smaller-diameter bores, particularly small-diameter bores having a relatively great length. Meanwhile, conventional small-bore-producing tools may be susceptible to chatter and tool deflection that may adversely affect bore size or finish. Thus, a need exists for a boring tool with sufficient rigidity to form bores having a high length-to-diameter ratio with great precision.
Another challenge that may be encountered during the use of conventional boring tools in the production of a bore having a relatively great length is the torque encountered by such tools while boring. Those of ordinary skill in the art will recognize that the production of a bore having a relatively great length may require the use of a tool that also has a relatively great length. Such tool length may provide a corresponding relatively great torque arm length, which would be a factor in the calculation of the amount of torque experienced by the tool. When a cutting member is engaged with the bore surface of a workpiece, normal forces exerted by the workpiece (e.g., in reaction to forces exerted by the tool) against the distal or cutting end of the tool may be the source of such torque. Such torque may be further increased if the tool is urged in a direction transverse its axis at its proximal end during cutting. Those of ordinary skill in the art will appreciate the adverse effects that such torque may produce (e.g. wear of tool, bending of tool, weakening of material or mechanisms at or near the torque pivot point, etc.). Accordingly, there exists a need for a tool that may be used to produce bores of relatively great length without the problems associated torque on the tool.
Conventional boring devices may also require time consuming adjustments to be retracted from a bore. For example, the tool retraction process may entail stopping tool spindle rotation, repositioning the tool, then finally retracting the tool from the bore. If another bore is to be produced, rotation of the tool must be initiated again, which also takes time. Of course, such a time consuming retraction routine may be undesirable when time is of the essence, such as in a mass production context. Thus, there exists a need for a tool that may be rapidly retracted from a bore, particularly without the need to stop rotation of the tool or reposition its axis of rotation.
Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings.